Chemical and spectroscopic analysis of olive mill waste water during a biological treatment

The treatment of olive mill waste water was studied on the laboratory scale. Physico–chemical analyses showed the final products had a mean pH of 5.4 without neutralisation and 5.7 when lime was added to the process. Raising the pH by adding lime had a positive outcome on the degradation of phenols, whose levels were reduced by over 76%. The lime also changed the structure of the organic matter, as seen in the infra-red spectra. Combining the FT-IR and 13C NMR data showed that with addition of lime, the density of aliphatic groups decreased to the benefit of aromatic groups, indicating that polymerisation of the organic matter occurred during the bioprocess. Under our experimental conditions, the biotransformation of olive mill waste water appears to favour the stabilisation of the organic matter through mechanisms analogous to those that lead to the formation of humus in the soil.